Double Trouble: Does Co-Morbid Chronic Somatic Illness Increase Risk for Recurrence in Depression? A Systematic Review. - Kok, Gemma D.; Bockting, Claudi L. H.; Burger, Huibert; Hannig, Wiebke; Pijnenborg, Gerdina H. M.; Cuijpers, Pim; Hollon, Steven D. (PLoS ONE, 2013)